Fix z-fighting on overlapping extrusions #3324
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This is a hard problem to solve. I think |
lucaswoj
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No clear way to address this at the moment, so I'll close for now as not actionable. |
astojilj
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May 24, 2022
Styleable layout property fill-extrusion-faux-ao (boolean). Implementation in shaders done under #ifdef FAUX_AO not to affect other use cases. This is a low cost approach that potentially combined with line-blur (TODO: line-blur artefacts issue #10000) provides plausible results, somewhat reminding of ambient occlusion. The approach shades vertical walls vertically near ground and horizontally near concave angles. In contrast to vertical-gradient that's linearly interpolated in fragment shader, exponential shading is exponential Implementation is specialized for scale of buildings. Open for later introduction of data constant paint property fill-extrusion-faux-ao-radius (in meters). E.g. defgault value of 3 would correspond to this implementation. Arguably, data visualizations on globe zoom levels benefit more from vertical-gradient that is linearly interpolated from ground to top than from this since in most of use cases there are no concave angles. Setting the property also activates an improvement for #3324 - z-fighting artefacts are especially noticeable on buildings. This improvement could be promoted to all the cases later. As it would take time to re-evaluate if the fix is acceptable for all the cases, it is enabled in shaders under #ifdef FAUX_AO. The appropach is based on common z-fighting culprits coming from overlapping fill extrusion walls that have different height and different base. In such case, higher planes and those with higher base (since often height is the same) are brought forward.
astojilj
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Jun 15, 2022
Styleable layout property fill-extrusion-faux-ao (boolean). Implementation in shaders done under #ifdef FAUX_AO not to affect other use cases. This is a low cost approach that potentially combined with line-blur (TODO: line-blur artefacts issue #10000) provides plausible results, somewhat reminding of ambient occlusion. The approach shades vertical walls vertically near ground and horizontally near concave angles. In contrast to vertical-gradient that's linearly interpolated in fragment shader, exponential shading is exponential Implementation is specialized for scale of buildings. Open for later introduction of data constant paint property fill-extrusion-faux-ao-radius (in meters). E.g. defgault value of 3 would correspond to this implementation. Arguably, data visualizations on globe zoom levels benefit more from vertical-gradient that is linearly interpolated from ground to top than from this since in most of use cases there are no concave angles. Setting the property also activates an improvement for #3324 - z-fighting artefacts are especially noticeable on buildings. This improvement could be promoted to all the cases later. As it would take time to re-evaluate if the fix is acceptable for all the cases, it is enabled in shaders under #ifdef FAUX_AO. The appropach is based on common z-fighting culprits coming from overlapping fill extrusion walls that have different height and different base. In such case, higher planes and those with higher base (since often height is the same) are brought forward.
astojilj
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Jun 20, 2022
Styleable layout property fill-extrusion-faux-ao (boolean). Implementation in shaders done under #ifdef FAUX_AO not to affect other use cases. This is a low cost approach that potentially combined with line-blur (TODO: line-blur artefacts issue #10000) provides plausible results, somewhat reminding of ambient occlusion. The approach shades vertical walls vertically near ground and horizontally near concave angles. In contrast to vertical-gradient that's linearly interpolated in fragment shader, exponential shading is exponential Implementation is specialized for scale of buildings. Open for later introduction of data constant paint property fill-extrusion-faux-ao-radius (in meters). E.g. defgault value of 3 would correspond to this implementation. Arguably, data visualizations on globe zoom levels benefit more from vertical-gradient that is linearly interpolated from ground to top than from this since in most of use cases there are no concave angles. Setting the property also activates an improvement for #3324 - z-fighting artefacts are especially noticeable on buildings. This improvement could be promoted to all the cases later. As it would take time to re-evaluate if the fix is acceptable for all the cases, it is enabled in shaders under #ifdef FAUX_AO. The appropach is based on common z-fighting culprits coming from overlapping fill extrusion walls that have different height and different base. In such case, higher planes and those with higher base (since often height is the same) are brought forward.
astojilj
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Jun 20, 2022
* Faux ambient occlusion specialized for buildings Styleable layout property fill-extrusion-faux-ao (boolean). Implementation in shaders done under #ifdef FAUX_AO not to affect other use cases. This is a low cost approach that potentially combined with line-blur (TODO: line-blur artefacts issue #10000) provides plausible results, somewhat reminding of ambient occlusion. The approach shades vertical walls vertically near ground and horizontally near concave angles. In contrast to vertical-gradient that's linearly interpolated in fragment shader, exponential shading is exponential Implementation is specialized for scale of buildings. Open for later introduction of data constant paint property fill-extrusion-faux-ao-radius (in meters). E.g. defgault value of 3 would correspond to this implementation. Arguably, data visualizations on globe zoom levels benefit more from vertical-gradient that is linearly interpolated from ground to top than from this since in most of use cases there are no concave angles. Setting the property also activates an improvement for #3324 - z-fighting artefacts are especially noticeable on buildings. This improvement could be promoted to all the cases later. As it would take time to re-evaluate if the fix is acceptable for all the cases, it is enabled in shaders under #ifdef FAUX_AO. The appropach is based on common z-fighting culprits coming from overlapping fill extrusion walls that have different height and different base. In such case, higher planes and those with higher base (since often height is the same) are brought forward. * AO: Replace faux-ao layout boolean by intensity and radius paint properties Instead of fill-extrusion-faux-ao layout constant property, 2 paint properties are introduced: - fill-extrusion-ambient-occlusion-intensity, in range [0..1] - fill-extrusion-ambient-occlusion-radius, in meter units, values larger than 0. Reasons: - is it too early top specify layout property that would be use as a hard switch of the feature. In future, we might have multiple types of AO (server side included) where type of AO would be used, not a boolean property. - separate properties intensity and radius are needed for globe zoom level visualization and those properties are expected when modelling AO, e.g. similar is found in Blender. * Fill extrusion z fighting render test, fill extrusion pattern support for AO With ambient occlusion intensity of 0.001, expected result is the same as with no ambient occlusion, but with z fighting fixed. * Render tests, process review comments. Shaders: removed sqrt and mix-es that are using constants Thanks @karimnaaji * Process review comments. Render tests for small angles * Link to documentation in shader code. Processing the latest comments and rebase.
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Extrusions (#3223) suffer from the same problem as #3320: when the map is pitched, extrusions at the same coordinate with different colors are z-fighting and flicker. Since we're drawing all elements in a bucket's element buffer in one draw call, there's currently no way to draw to the depth buffer at a higher resolution (per feature). We should investigate drawing to the depth buffer per-feature or based on actual z index in↕️ space…
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